1. Field of the Invention
Disclosed herein is a rotary earth boring drill bit and the method of manufacture of such a bit, and in particular, a rotary fixed cutter drill bit suitable for use in drilling boreholes into the earth for oil and/or gas exploration and production.
Earth boring drill bits are well known and used for drilling through earthen formations for mineral exploration and extraction, and in particular hydrocarbons. One particular type of earth boring drill bit has an infiltrated metal matrix body. This type of drill bit may be manufactured by packing a mould that has a negative pattern of the bit form with metal powder, such as tungsten carbide powder, around a metal (typically steel) blank. This assembly is then infiltrated with a molten binding alloy in a high temperature furnace process.
For each design of a drill bit, a mould must be built for forming the body of the bit. Then the blank may typically be suspended in the mould, as the metal powders are added. The assembly is then typically furnaced until the mass reaches a fairly uniform temperature of greater than about 1900 F in its center, which causes the metal binder to melt. Upon cooling, the metal binder solidifies, fusing the assembly into a sold mass. Upon cooling, the metal pin section may be threaded for attachment to a drill string.
Conventionally, a bit mould may be fabricated by machining hard graphite material, or pressing soft mud (Graphite/clay) material in a graphite pot using a pattern. Another method for manufacturing a bit mould is to employ direct layered manufacture techniques. In the operation, the layered manufacturing equipment sinters or otherwise secures a first layer of particles of mould material together, disposes a second layer of particles over the first layer, sinters particles in selected regions of the second layer together and to the first layer, and repeats this process to fabricate subsequent layers until the mould has been formed from the mould material particles.
Other known methods for manufacturing fixed cutter drill bits include machining the bit bodies from steel (or other metallic) blanks. Rather than a matrix type bit body with impregnated diamond grains, a solid metallic bit body may be machined from one of more blocks of metal, preferably steel, and a series of cutting elements may be mounted upon the bit's body. As described above, such cutting elements may take the form of polycrystalline diamond compact cutters in which a table of polycrystalline diamond is bonded to a substrate of less hard material, for example tungsten carbide, which, in turn, is mounted upon the steel bit body.
2. Description of the Related Art
Known layered manufacture techniques for making sand moulds include inject glue printing technology and laser sintering technology. The printing technique selectively dispenses the resin in the layered sand material. The activator contained in the sand hardens the binder and realizes the object one layer at a time from bottom to top. In the laser sintering process, the laser selectively sinters coated sand material by scanning cross-sections generated from a CAD file on the surface of a process platform. After each cross-section is scanned, the platform is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.
U.S. Pat. No. 6,353,771 and GB Patent application 231545 claim a method to use a layering device to build a mould for a drill bit using solid and conventional sand moulds. The present invention is drawn to a thin wall, hollow and fill type of mould with high thermal conductive material sand mould. This type of sand mould increases heating rates during infiltration process and direction solidification during cooling reducing the propensity for casting defects such a macro and micro porosity and blank-matrix disbond. The high thermal conductive sand mould shell essentially permits the fabrication of matrix bit body with a casting quality that is superior to convention printed sand molds.